Anaerobic digestion system capable of automatically discharging slag and control method
Technical Field
The invention relates to the technical field of anaerobic digestion equipment, in particular to an anaerobic digestion system capable of automatically discharging slag and a control method.
Background
China is a big agricultural country and a big population country, and generates a large amount of organic wastes such as straws, livestock and poultry manure, domestic garbage and the like every year, if the organic wastes are not properly treated in time, the problem of serious environmental pollution can be caused. The anaerobic digestion technology is an effective way for treating organic wastes, the method not only can realize the harmless and quantitative reduction treatment of the organic wastes, but also can produce renewable clean energy, namely methane, so that the energy utilization problem in rural areas can be solved according to local conditions, the energy structure is improved, the living environment in rural areas is improved, in addition, the fermentation residues are rich in nutrition, and the fermentation residues can also be used as fertilizers to be applied to farmlands.
The anaerobic digestion technology is a good organic waste resource utilization technology, and can treat various organic raw materials such as straws, livestock and poultry manure, household garbage and the like. During the collection process of the fermentation raw materials, due to the complex and various types and components of the raw materials and the great difference of the production conditions and environments, some solid pollutants (such as sand, stones and other solids which cannot be digested anaerobically) are often entrained in the mixed raw materials. In the operation process of the anaerobic digestion reactor, the solid pollutants are often precipitated to the bottom of the reactor gradually due to relatively high density, so that the effective volume of the reactor is reduced, sometimes even the normal operation of the anaerobic digestion reactor is disturbed, and the solid pollutants are required to be removed in time. Typically, these solid contaminants are periodically removed by emptying the reactor and cleaning the bottom of the reactor of the sediment. Because the anaerobic digestion reaction is a complex biochemical reaction process, the time from starting debugging to stable operation of the reactor is 5-10 days or even longer, and if the reactor is stopped to be cleaned, the operation efficiency of the engineering is directly influenced, and the engineering benefit is reduced.
Disclosure of Invention
One of the objectives of the present invention is to provide an anaerobic digestion system with automatic slag discharge, which can automatically clean the sediment at the bottom of the main reactor to increase the effective volume of the main reactor and further increase the operation efficiency and the engineering benefit of the project.
The second purpose of the present invention is to provide a control method for an anaerobic digestion system with automatic slag discharge, which ensures that the sediment material (non-degradable material, i.e. solid pollutant) at the bottom of the main reactor is discharged from the main reactor to the secondary reactor rapidly and intensely in a short time, thereby realizing the discharge of the sediment material at the bottom of the main reactor.
The technical scheme adopted by the invention is as follows:
an anaerobic digestion system capable of automatically discharging slag comprises a main reactor, wherein the main reactor is communicated with a secondary reactor through a slag discharge pipe at the bottom; the slag discharge pipe is provided with a flow control valve; one end of the discharge pump is communicated with the bottom of the secondary reactor, and the other end of the discharge pump is connected with an inlet of the solid-liquid separation device; the upper parts of the main reactor and the secondary reactor are respectively provided with a biogas pipe I and a biogas pipe II.
The height of the secondary reactor is higher than or equal to that of the main reactor.
The liquid level I of the materials in the main reactor is higher than the liquid level II of the materials in the secondary reactor.
And an air inlet pipe and a gas pressure gauge are arranged below the top cover of the main reactor.
The bottom of the main reactor is provided with a tank bottom frustum positioned in the center and a tank bottom slope positioned at the edge, and an annular groove is formed between the tank bottom frustum and the tank bottom slope; the pipe orifice of the slag discharge pipe points to the annular groove.
The mouth of the slag discharge pipe is in a bell mouth shape.
And a water collecting pit is arranged at the bottom of the main reactor.
A control method of an anaerobic digestion system with automatic slag discharging function comprises the steps that a feeding pump continuously or periodically pumps organic garbage, straws and livestock and poultry manure fermentation raw materials into a main reactor, after the main reactor is operated in a conventional mode to generate biogas and fermentation residues, when the liquid level in the main reactor reaches a preset position, a flow control valve is opened, the flow rate of materials flowing out of the main reactor is 500-5000 m3/h, the flow rate of materials flowing out of a secondary reactor is 2-200 m3/h, the opening time of the flow control valve is kept to be 8-15 s, and solid materials deposited at the bottom of the main reactor are discharged.
The flow control valve was opened to set the flow rate of effluent from the primary reactor at 1200m3/h and the flow rate of effluent from the secondary reactor at 10m3/h, maintaining the open time of the flow control valve at 10 s.
Closing a biogas pipe I of the main reactor to accumulate biogas at the top in the main reactor to form pressure; or introducing marsh gas into the main reactor from the gas inlet pipe, and opening the flow control valve to discharge residue after pressure is formed.
The invention adopts a two-stage reactor design, namely a main reactor and a secondary reactor, wherein the secondary reactor can regularly clean solid pollutants (non-degradable solid matters such as sand, stones and the like) in the main reactor, thereby greatly reducing the times that the main reactor needs to stop running to clean sediments, increasing the stable running time and further improving the engineering benefit; the effective volume of the reactor can be improved and the operation efficiency can be improved by regularly cleaning the sediment at the bottom of the main reactor; the materials discharged from the main reactor can be continuously subjected to anaerobic digestion in the secondary reactor to generate more biogas, so that the engineering benefit is increased.
2. The slag discharging pipe is designed to be bent towards the bottom of the tank in the main reactor, and the port is flared, so that materials with higher concentration (namely, higher content of solid pollutants) can be discharged from the main reactor, and the slag discharging efficiency is improved.
3. The bottom of the main reactor forms an annular groove area between the tank bottom frustum and the tank bottom slope, and the relatively dense solid pollutants settled to the bottom in the fermentation process are guided inwards by the tank bottom boss and the tank bottom slope and enter the groove area, so that the solid pollutants are more concentrated, and the slag discharge efficiency is further improved.
4. The anaerobic digestion system of the present invention, in which the main reactor is continuously cleaned, can be operated with relatively higher efficiency, compared to an anaerobic digestion system in which no secondary reactor is provided.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a cross-sectional view A-A of FIG. 1;
in the figure: the device comprises a main reactor 1, an air inlet pipe 2, a double-layer membrane type gas storage cabinet 3, a methane pipe I4, a liquid level I5, a side stirring device 6, a secondary reactor 7 (or a buffer tank), a central stirring device 8, a methane pipe II9, a liquid level II10, a discharge pump 11, a solid-liquid separation device 12, a flow control valve 13, a water collecting pit 14, a slag discharge pipe 15, a tank bottom boss 16, a tank bottom plane 17, a tank bottom slope 18 and a liquid level sensor 19.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
Referring to fig. 1, the anaerobic digestion system with automatic slag discharge comprises a main reactor 1, wherein the main reactor 1 is communicated with a secondary reactor 7 through a slag discharge pipe 15 at the bottom; the slag discharge pipe is provided with a flow control valve 13; the flow control valve 13 is used to allow or prevent the passage of material fluid. One end of a discharge pump 11 is communicated with the bottom of the secondary reactor 7, the other end of the discharge pump is connected with an inlet of a solid-liquid separation device 12, the discharge pump 11 is used for conveying materials from the secondary reactor to the solid-liquid separation device 12, the solid-liquid separation device 12 is used for separating fermentation residues into solid materials (biogas residues) and liquid materials (biogas slurry), and the biogas residues and the biogas slurry can be used as organic fertilizers after being properly treated. The upper parts of the main reactor 1 and the secondary reactor 7 are respectively provided with a biogas outlet pipe I4 and a biogas outlet pipe II9, and the opening positions of the biogas outlet pipe I4 and the biogas outlet pipe II9 are respectively higher than the liquid level I5 and the liquid level II10 in the respective reactors. The anaerobic digestion system of the present invention, in which the main reactor is continuously cleaned, can be operated with relatively higher efficiency, compared to an anaerobic digestion system in which no secondary reactor is provided.
The diameter of the secondary reactor 7 is 1.2-2.5 m, and the height is higher than or equal to that of the main reactor. Therefore, even if the flow control valve fails, the secondary reactor can be filled without overflowing after the materials in the main reactor are discharged into the secondary reactor.
The size of the main reactor is determined according to actual needs. The volume of the secondary reactor can meet the requirement of material discharge amount of the main reactor at least once, the secondary reactor is not in a linear relation with the volume of the main reactor, and when the volume of the main reactor is larger, the slag discharge time or frequency of bottom materials can be increased.
The level of feed in the primary reactor 1, I5, was higher than the level of feed in the secondary reactor 7, II 10. And a liquid level height difference is formed, so that the discharge of bottom materials is facilitated. The height of the liquid level I of the main reactor is determined by the feeding amount of the reactor and is controlled by a level sensor 19; the height of the level II of the secondary reactor is determined by the amount of material discharged from the main reactor.
The reactor is characterized in that a plurality of side stirring devices 6 are arranged on the circumference direction below the top cover of the main reactor 1, the secondary reactor 7 is provided with a central stirring device 8, and the stirring devices are used for uniformly mixing materials in the reactor, so that the material conversion efficiency and the reactor operation efficiency are improved.
An air inlet pipe 2 and a gas pressure gauge are arranged below a top cover of the main reactor 1, and the mounting positions of the air inlet pipe 2 and the gas pressure gauge are higher than the liquid level I of the main reactor, so that the function of utilizing air pressure to discharge slag is achieved, and the automatic slag discharge effect is enhanced.
A double-layer soft film type gas storage cabinet 3 is arranged above the top cover of the main reactor 1 and used for storing methane, a methane outlet pipe I4 is arranged on the double-layer soft film type gas storage cabinet, and the flexible film is used as a flexible top cover of the reactor, so that the opening is relatively convenient, and the maintenance of the reactor is facilitated; the weight is light, and the construction cost is low; the air tightness is good, and the gas is not easy to diffuse; the pressure of the outlet methane is constant.
Referring to fig. 1 and 2, the bottom of the main reactor 1 is provided with a tank bottom frustum 16 positioned at the center and a tank bottom slope 18 positioned at the edge, and an annular groove 17 is formed between the two; the pipe orifice of the slag discharge pipe 15 points to the ring groove 17. The relatively dense solid contaminants (such as sand, rocks, etc.) that settle to the bottom of the main reactor during fermentation will be directed inwardly by the tank bottom cone 16 and the tank bottom slope 18 and into the annular groove 17, thereby further concentrating the solid contaminants at the bottom of the main reactor. And the slag discharge pipe 15 and the discharge pump 13 are used for continuously pumping outwards, so that at least part of sediment (non-degradable solid matters) at the bottom of the reactor can be removed under the condition of not interrupting the anaerobic digestion process (namely not stopping the operation of the reactor), the effective volume of the reactor is increased, the continuous operation time of the engineering is prolonged, the normal operation of an anaerobic digestion system is not substantially interfered, and the operation benefit of the engineering is improved. The original discharge system of the main reactor still exists in the embodiment.
The mouth of the slag discharge pipe 15 is in a bell mouth shape, so that the sediment substances can be conveniently extracted.
The bottom of the main reactor 1 is provided with a water collecting pit 14 to facilitate the discharge of materials in the main reactor.
In the above embodiment, the original normal discharge system of the main reactor still exists, and is used for normal daily feeding and discharging.
A control method of anaerobic digestion system with automatic slag discharge comprises continuously or periodically pumping organic garbage, straw, livestock and poultry manure fermentation raw materials into a main reactor 1 by a feed pump, wherein after the main reactor 1 is operated in a conventional mode to generate biogas and fermentation residues, the biogas is gathered at the top of the reactor and deforms a flexible membrane to form a gas storage space, and the biogas can be discharged by controlling a valve on a biogas pipeline; the material level sensor 19 arranged in the main reactor 1 is used for controlling the material amount in the main reactor, when the liquid level in the main reactor 1 reaches a preset position, the flow control valve 13 is opened, so that the flow rate of the material flowing out of the main reactor is 500-5000 m3/h, the flow rate of the material flowing out of the secondary reactor is 2-200 m3/h, and the opening time of the flow control valve 13 is kept to be 5-20 s; the method is further optimized as follows: the flow rate of the material flowing out of the main reactor is 1000-1600 m3/h, the flow rate of the material flowing out of the secondary reactor is 5-20 m3/h, and the opening time of the flow control valve 13 is kept to be 8-15 s; the further optimization is as follows: the flow rate of the effluent from the primary reactor was set at 1200m3/h, the flow rate of the effluent from the secondary reactor was set at 10m3/h, and the opening time of the flow control valve 13 was kept at 10s. Through the control of the flow rate of the flow control valve, the nondegradable solid matters with large density can be discharged from the main reactor to the secondary reactor in a short time, and the cleaning and discharging of the deposited materials at the bottom of the reactor are realized. The slag discharge time of the flow control valve (the opening time of the flow control valve) is set to be short enough to discharge the sediments at the bottom of the main reactor, so that the sediments can flow rapidly with high strength to carry sands, stones and the like, and the discharged materials are mainly bottom sediments (namely, the content of solid pollutants is relatively high) rather than a large amount of fermented materials. The flow of material from the secondary reactor is much slower than in the primary reactor. Because a small amount of materials containing precipitates are discharged from the main reactor to the secondary reactor every time, the concentration of the materials in the secondary reactor is much higher than that of the materials in the main reactor, and the materials discharged from the main reactor can be continuously subjected to anaerobic digestion in the secondary reactor to generate more biogas. The contents of the secondary reactor may be periodically or continuously fed at a relatively low flow rate (e.g., 10 m)3And/h) pumping out, and further carrying out solid-liquid separation and post-treatment for utilization. Because the secondary reactor is small in size, the tank is easier to evacuate and the tank bottom is easier to clean, and the normal operation of the main reactor is not influenced. By this purging operation, the main reactor can be kept in a good operating state, thereby improving the operating efficiency.
The invention aims to enhance the automatic slag discharging effect and increase the function of discharging slag by utilizing air pressure: closing a biogas pipe I4 of the main reactor 1 to accumulate biogas at the top of the main reactor to form pressure (such as 30-60 kPa); or introducing biogas into the main reactor 1 from the gas inlet pipe 2, forming pressure, and then opening the flow control valve 13 to discharge slag. When the flow control valve is opened, the material can be discharged more quickly and effectively under the further action of the gas pressure. The method is simple and convenient to operate, reasonable in structure, economical and practical.